The present invention relates to a system for detecting operating parameters of the throttle valve, such as angular velocity which is used in an emission control system for internal combustion engines.
The emission control system with a three-way catalyst converter as in U.S. Pat. No. 4,132,199 is provided with an oxygen sensor to sense the oxygen content of exhaust gases to generate an electrical signal as an indication of the air-fuel ratio of the air-fuel mixture supplied to the engine. The control system operates to detect whether the feedback signal from the oxygen sensor is higher or lower than the stoichiometric value, for producing an error signal and to control the air-fuel ratio of the mixture to be induced into the engine in accordance with the error signal. Such a feedback control system inherently oscillates due to the detection delay of the oxygen sensor, the control delay in the system. The oscillation of the system causes the variation of the controlled air-fuel ratio relative to the stoichiometric value. Such a variation is increased during an acceleration condition of the engine and the control operation is greatly delayed during such a condition.
Consequently, the emission control cannot accomplish the desired reduction of the harmful constituents of the exhaust gases. In order to compensate for this, it is necessary to detect operating parameters such as the angular velocity, angular acceleration, duration or opening angle of the throttle valve.